Getting motor amperage value to my PLC

[PLC Pie Guy]

Hey there.
I am wondering how I would go about geting motor current value from A powerflex 40 connected over ethernet/ip (22_Comm_E) to my compact loix V16 controller. My drive is updating and recieving update data from pre-defined module data type tags. One is ABowerflex_40_Drive_4Bytes:O:0 the other is
ABowerflex_40_Drive_8Bytes:I:0.
I have done a couple projects using implicit messaging. Would an explicit message be the proper way to go about getting the info I desire or is there some way to get that data coming through one of my module_defined tags.
Can I message a drive that is already communicating in the fashion I have described?

Thanks for any assistance.

 

[FactoryTalktotheHand]

Yes. You can explicit message to the drive and read any parameter, including the current draw. I've done this before but it's been a long time. I'd consult the 22-Comm-E manual for this. There's a huge, weird offset that I can't remember and it changes depending on how many drives you have connected to the Comm-E. Like for instance I was trying to read parameter 3 on Drive 2 and the address I was reading was something like 17384.

Not related, but one of the things I really like about the Powerflex 525 is that it allows you to specify up to 4 additional input and output parameters to include in the implicit messaging block. Makes things a LOT simpler.

 

[dmargineau]

Your application's hardware defined (PF40+22-COMM-E) four Input words (8 bytes) of the 22-COMM-E module contain the Logic Status (bit examined)and Feedback(word examined) of the PF40 plus two "overhead" words needed by the 1756 ENet/IP bridge.
Page 4-5 of
http://literature.rockwellautomation.com/idc/groups/literature/documents/um/22comm-um004_-en-p.pdf
You should be able to implement explicit messaging between the CLX controller and the 22-COMM-E adapter using the examples in Chapter 6, Page 6-1 of
http://literature.rockwellautomation.com/idc/groups/literature/documents/um/22comm-um004_-en-p.pdf
while pointing to the PF40 parameters you wish to "retrieve" within the RSL5K application.

 

[PLC Pie Guy]

Hey there.
In my case I only have one drive per 22-comm-e card. So that made it easy to determine the instance portion of the MSG instruction. Using the example in the book for class and atribute I was able to set this up successfully. What I need to do now is get a better understanding of class and atribute values.
I asked the question about adding an explicit message to the drive because I was not certain about messaging a drive that is already communicating its parameters to the PLC. I just wanted to be sure I wouldn't affect the control of the drive.

I have set the message up using a 1000 pre set TON that is free running. I use a limit instruction to enable one message between 0 and 250 and a message to another drive (for the same par.) to LIM between 250 and 500. Does that seem adaquit to get up to date info without flodding my network?

Thanks

 

[OkiePC]

If everything is happy and talking normally, you don't need to keep triggering the message every scan within your time limit ranges. I would program to only occur on the rising edge of each limit range. I normally program continuous "round robin" repeating msg instructions to fire only once per device per time period.

See example MSG instruction on page 5:
http://literature.rockwellautomation.com/idc/groups/literature/documents/ap/1756-ap002_-en-e.pdf

As soon as the MSG is ENabled, it will be skipped on the next scan. But, the MSG is still going to be fired off, and will either ERror or get DoNe very quickly in most cases, although a timeout error can take awhile. Then the EN bit drops out, and the rung can go true again, but if you stop asking for that piece of data was it is DN or errored for that period, you are not constantly queueing up new messages, only one per time period per device at its ranged period rising edge.

The examples are oversimplified, usually you do need to account for errors and utilize the EN and DN bits in your message trigger logic.